ABSTRACT
Optical properties of CdAl2Se4, CdAl2Se4:Co2+ and CdAl2Se4:Er3+ single crystals grown by the chemical transport reaction method were investigated by the measurements of optical absorption and photoluminescence. In the optical absorption spectrum at 13 K of CdAl2Se4:Co2+ single crystals, we observed the impurity absorption bands due to the electronic transitions of 4A2(4F)→ 4T1(4F) and 4A2(4F)→ 4T1(4P) of Co2+ ions with Td symmetry of the host lattice. Two broad blue-green photoluminescence bands, centered at 458 and 539 nm in the photoluminescence spectrum at 10 K of CdAl2Se4 were observed and explained as due to donor-acceptor pair recombination. The band model for the photoluminescence mechanism of CdAl2Se4 was suggested. For CdAl2Se4:Er3+ on the other hand, we observed several groups of sharp photoluminescence peaks due to emission transitions between the energy levels of Er3+ ions with Td symmetry sites.
